The present invention relates to environmental control systems (ECSs), and more particularly to an air cycle machine (ACM) configuration.
ECSs provide a supply of conditioned air to an enclosure, such as an aircraft cabin and cockpit. Conventional ECSs have utilized an air-to-air cycle cooling system which is in a heat exchange relationship with a liquid loop. The liquid loop typically cools other heat loads such as avionics packages. Interaction between the air and liquid subsystems is relatively complex. Moreover, airflow sequencing, particularly for multi-turbine air cycle machines (ACMs), radically affects ECS efficiency. In many instances much thermal energy may be wasted or otherwise inefficiently used.
In one conventional system, a flow of bleed air is taken from an intermediate or high pressure stage within a jet engine. The bleed air is pre-cooled within an air-to-air heat exchanger with heat being rejected to RAM air and then flowed to a compressor of the ACM. After compression, the air is routed through a second air-to-air heat exchanger, a regenerative heat exchanger and an air-to-air reheater heat exchanger. Condensed water vapor is extracted by a water extractor, and dehumidified air is routed to a turbine. Expanded air from the turbine flows through another water collector and into a liquid-to-air heat exchanger of the liquid loop. A relatively warmer liquid in the liquid loop which is used to cool the avionics is thereby cooled. From the liquid-to-air heat exchanger, the air passes through the reheater heat exchanger. The dehumidified air is then passed into a second turbine of the ACM where it is again expanded and passed through another liquid-to-air heat exchanger to further absorb heat from the liquid loop.
The ACM is an integral part of the ECS. Conventional ACMs include a rotative assembly surrounded by a static structure. Typically, conventional ACMs include two turbines, a compressor, and a fan. Conventional ACMs locate the two turbines, compressor, and fan on a single shaft. Due to the unique operation and installation requirements of the RAM system, the fan rotor is located on one outboard end of the ACM which may reduce the efficiency thereof. This may reduce the efficiency of the entire ECS system.